Enzyme-linked immunoabsorbent assays have been developed to detect and quantitate a number of viral bacterial and fungal antigens and antibodies as well as DNA. During the past year we have completed studies indicating that influenza A hemagglutinin can be reliably detected in clinical specimens and used as a rapid means of diagnosis. In addition assays have been successfully used for typing of pneumococci and for evaluating the clinical immune response of splenectomized patients to penumococcal vaccine.